Takashi Yamazaki is a student in Sakura Kinomoto's class, and the only male student in the class to be referred to by name before the introduction of Syaoran Li. The character is named after film director, Takashi Yamazaki, who is a friend of the series creators, CLAMP. Throughout the series, Yamazaki's defining trait is his ability to fabricate highly detailed fake stories and histories about practically any subject. While most of his classmates see through these fabrications, Sakura and Syaoran often believe them. When the character Eriol Hiiragizawa is introduced in the second half of the series, he becomes Yamazaki's storytelling ally. The two are able to respond to one another's clues perfectly and spin complex stories on the fly.

Fellow classmate Chiharu Mihara often interrupts his stories so others know when he is lying, and proceeds to punish him for lying by pretending to strangle him or by dragging him away by his collar. While the two often seem to be arguing, they are actually a couple and have known one another since kindergarten. She is the only girl in the series that he addresses by her first name. Despite Yamazaki's often joking nature, he is shown to have a serious and sensitive side as well, willing to jump into a fierce wave to attempt to save fellow classmate Rika from drowning, and leaving Chiharu alone to talk to Sakura when Sakura was struggling with her feelings for Syaoran.

In the anime adaptation, Yamazaki is the only character to be rarely shown with his eyes open. His relationship with Chiharu is left more ambiguous, though on the day of Judgement when Sakura is shown a world in which everyone losing their feelings for the person they love the most, Yamazaki and Chiharu lose their feelings for each other and are shown to be strangers.

In the Cardcaptors English adaptation, Yamazaki's name is changed to Zachary Marker and all hints of his relationship with Chiharu are removed. Instead, they are said to be cousins and the Chiharu's joking strangling of Yamazaki is considered to be sibling rivalry.

Yamazaki is voiced by Issei Miyazaki in the anime adaptation, and by Philip Pacaud in Cardcaptors. In the English dub of the second film, he is voiced by Joshua Seth.